1. Technical Field of the Invention
This invention relates to the field of inkjet printheads and printing apparatuses and, in a particular embodiment, to the production of printheads having a polyimide as a photoresist for the thick flow features which adheres to a nozzle plate of polyimide or other materials, without the use of an adhesive material between the two surfaces.
2. General Background of the Invention
In the art of inkjet printing, inkjet printheads utilize semiconductor chips which are electrically activated to eject ink droplets on demand through nozzle holes in a nozzle plate attached to the chips. The ink ejection devices are located in close proximity to the ink feed via or slot along opposing sides. In order for the inkjet nozzles to perform optimally, higher firing frequencies of the inkjet nozzles are needed, to produce higher print speed and better resolution. In order to obtain this goal, there is a need to implement flow features into the photoresist on the wafer, instead of in the adhesive used to bind the nozzle plate. This type of process is currently referred to as thickfilm flow features. The thickfilm flow feature photoresist must have a high enough glass transition temperature (Tg) to withstand all of the other heat processes, minimal hydrofluoric acid (HF) production, superior adhesion, and great durability in the presence of the ink.
In U.S. Pat. No. 6,540,334, assigned to Lexmark International, Inc., the thickfilm layer applied to the chip provides a surface for attachment of a nozzle plate to the upper surface of the chip. In the prior art, such as U.S. Pat. No. 6,540,334, the thickfilm layer is derived from a radiation and/or heat curable polymeric film preferably containing a difunctional epoxy material, a polyfunctional epoxy material, and suitable cure initiators and catalysts. The disclosure of U.S. Pat. No. 6,540,334 is incorporated herein by reference.
Using an epoxy material such as disclosed in U.S. Pat. No. 6,540,334 requires additional nozzle plate adhesives and increases the overall height of the nozzle plate stackup, which does not allow high firing frequencies.
The following U.S. Patents, and all patents mentioned herein, are incorporated herein by reference:    U.S. Pat. Nos.: 5,010,355; 5,534,901; 5,686,224; 5,869,595; 5,907,333; 6,151,042; 6,260,956; 6,409,316; 6,485,130; 6,540,334; 4,130,600; 4,626,474; 5,162,140; 5,260,130; 5,457,149; 5,510,425; 5,859,155; 6,054,509; 6,214,460; 6,518,362.